Liquid crystal composition and liquid crystal display device

ABSTRACT

A liquid crystal composition having a negative dielectric anisotropy and containing at least one compound selected from a group of compounds represented by formula (1) as a first component, at least one compound selected from a group of compounds represented by formula (2) as a second component, at least one compound selected from a group of compounds represented by formula (3) as a third component, and at least one compound selected from a group of compounds represented by formula (4) as a fourth component:  
                 
 
wherein the liquid crystal composition consists essentially of the first component, the second component, the third component and the fourth component and wherein R 1  is alkyl or alkenyl; R 2  is alkyl or alkoxy; R 3  is alkyl or alkoxymethyl; R 4  is alkyl; A 1  is 1,4-cyclohexylene or 1,4-phenylene; A 2  is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenhlene; and Z 1  is a single bond or —COO—.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. JP 2005-204329, filed Jul. 13, 2005, whichapplication is expressly incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a liquid crystal composition suitable for usein an AM (active matrix) device and an AM device containing thecomposition. In particular, the invention relates to a liquid crystalcomposition having a negative dielectric anisotropy and a device havingan IPS (in-plane switching) mode or a VA (vertical alignment) modecontaining the composition.

2. Related Art

In a liquid crystal display device, classification based on an operatingmode of liquid crystals includes phase change (PC), twisted nematic(TN), super twisted nematic (STN), electrically controlled birefringence(ECB), optically compensated bend (OCB), in-plane switching (IPS),vertical alignment (VA), and so forth. Classification based on a drivingmode includes a passive matrix (PM) and an active matrix (AM). PM isfurther classified into static, multiplex and so forth, and AM isclassified into a thin film transistor (TFT), a metal insular metal(MIM) and so forth. TFT is further classified into amorphous silicon,polycrystal silicon and continuous grain silicon. The polycrystalsilicon is classified into a high temperature type and a low temperaturetype according to a production process. Classification based on a lightsource includes a reflection type utilizing natural light, atransmission type utilizing a backlight, and a semi-transmission typeutilizing both natural light and a backlight.

These devices contain a liquid crystal composition having suitablecharacteristics. General characteristics of the composition should beimproved to obtain an AM device having good general characteristics.Table 1 below summarizes the relationship between the generalcharacteristics of the composition and the AM device. The generalcharacteristics of the composition will be explained further based on acommercially available AM device. The temperature range of a nematicphase relates to the temperature range, in which the device can be used.The desirable maximum temperature of a nematic phase is approximately70° C. or more, and a desirable minimum temperature of a nematic phaseis approximately −20° C. or less. The viscosity of the compositionrelates to the response time of the device. A short response time isdesirable for displaying a moving image. Accordingly, a small viscosityof the composition is desirable. A small viscosity at a low temperatureis more desirable. TABLE 1 General characteristics of liquid crystalcomposition and AM device General Characteristics of GeneralCharacteristics of No a Composition an AM Device 1 Temperature range ofa nematic Usable temperature range is wide phase is wide 2 Viscosity issmall¹ Response time is short 3 Optical anisotropy is suitable Contrastratio is large 4 Dielectric anisotropy is large Driving voltage is low,electric in positive or negative power consumption is small 5 Specificresistance is large Voltage holding ratio is large and a contrast ratiois large¹A liquid crystal composition can be injected into a cell in a shorttime.

The optical anisotropy of the composition relates to the contrast ratioof the device. Devices having a VA mode, an IPS mode, and so forthutilize electrically controlled bireflingence. In order to maximize acontrast ratio of a device having a VA mode, an IPS mode, and so forth,a product (Δn·d) of the optical anisotropy (Δn) of the composition andthe cell gap (d) of the device is designed to be a constant value.Examples of the value include from approximately 0.30 μm toapproximately 0.35 μm (VA mode) and from approximately 0.20 μm toapproximately 0.30 μm (IPS mode). Since the cell gap (d) is generallyfrom approximately 3 μm to approximately 6 μm, the optical anisotropy ofthe composition is generally from approximately 0.05 to approximately0.11. A large dielectric anisotropy of the composition contributes to asmall driving voltage of the device. Accordingly, a large dielectricanisotropy is desirable. A large specific resistance of the compositioncontributes to a large voltage holding ratio and a large contrast ratioof the device. Accordingly, a composition having a large specificresistance is desirable at room temperature and also at a hightemperature in the initial stage. A composition having a large specificresistance is desirable at room temperature and also at a hightemperature after use for a long period of time. Since an ultravioletray is used on producing a device, a composition having a large specificresistance is desirable at room temperature and also at a hightemperature after irradiation with an ultraviolet ray.

A composition having a positive dielectric anisotropy is used in an AMdevice having a TN mode. On the other hand, a composition having anegative dielectric anisotropy is used in an AM device having a VA mode.A composition having a positive or negative dielectric anisotropy isused in an AM device having an IPS mode. A liquid crystal compositionhaving a negative dielectric anisotropy is disclosed in the followingpatent documents: JP H10-176167 A/1998, JP 2000-96055 A/2000, JP2001-354967 A/2001 and JP 2003-13065 A/2003.

SUMMARY OF THE INVENTION

The invention relates to a liquid crystal composition having a negativedielectric anisotropy and containing at least one compound selected froma group of compounds represented by formula (1) as a first component, atleast one compound selected from a group of compounds represented byformula (2) as a second component, at least one compound selected from agroup of compounds represented by formula (3) as a third component, andat least one compound selected from a group of compounds represented byformula (4) as a fourth component,

wherein the liquid crystal composition consists essentially of the firstcomponent, the second component, the third component and the fourthcomponent and wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³is alkyl or alkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or1,4-phenylene; A² is 1,4-cyclohexylene, 1,4-phenylene or2-fluoro-1,4-phenhlene; and Z¹ is a single bond or —COO—.

The inventions also relates to a liquid display device comprising theliquid crystal composition, and so forth.

DETAILED DESCRIPTION OF THE INVENTION

The liquid crystal composition of the invention or the liquid crystaldisplay device of the invention may occasionally be expressed simply as“the composition” or “the device,” respectively. A liquid crystaldisplay device is a generic term for a liquid crystal display panel anda liquid crystal display module. The main components of the liquidcrystal composition are liquid crystal compounds. The liquid crystalcompound is a generic term for a compound having a liquid crystal phasesuch as a nematic phase at 25° C., a smectic phase at 25° C. and soforth, and also for a compound having no liquid crystal phase at 25° C.but being useful as a component of a composition. The phrase “at leastone compound selected from a group of compounds represented by formula(1)” may be abbreviated to “the compound (1).” The other formulas areapplied with the same rule.

The term “at least one compound selected from a group of compoundsrepresented by formulas (1) and (2)” has three meanings, i.e., a casewhere a compound is selected only from a group of compounds representedby formula (1), a case where a compound is selected only from a group ofcompounds represented by formula (2), and a case where a compound isselected from a group of compounds represented by both of formulas (1)and (2). The other formulas are applied with the same rule.

The term “essentially” means that the composition is primarily, but notexclusively, constituted by compounds selected from the compounds (1) to(4) but that the composition may further contain other compounds (e.g.,an additive, an impurity, and so forth). The additive can includeoptically active compounds, antioxidant compounds, coloring matters, andso forth. The impurity is a compound and so forth contaminated in theprocess such as the synthesis of a component compound and so forth.

In the case where the first component is a single compound, the term“the ratio of the first component” means the ratio of the compound. Inthe case where the first component includes two or more compounds, itmeans the total ratio of the compounds constituting the first component.The other components are applied with the same rule.

The term “at least one compound selected from the group of compoundsrepresented by formula (2-2) as the second component” means that thesecond component is selected only from formula (2-2), and the secondcomponent does not contain other compounds than those of formula (2-2).The other components and the other formulas are applied with the samerule.

A higher limit of a temperature range of a nematic phase may beabbreviated to “a maximum temperature.” A lower limit of a temperaturerange of a nematic phase may be abbreviated to “a minimum temperature.”“A specific resistance is large” means that the composition has a largespecific resistance at room temperature and also at a high temperaturein the initial stage, the composition has a large specific resistance atroom temperature and also at a high temperature even after it has beenused for a long time, and the composition has a large specificresistance at room temperature and also at a high temperature even afterit is irradiated with an ultraviolet ray. “A voltage holding ratio islarge” means that an device has a large voltage holding ratio at roomtemperature and also at a high temperature in the initial stage, thedevice has a large voltage holding ratio at room temperature and also ata high temperature even after it has been used for a long time, and thedevice has a large voltage holding ratio at room temperature and also ata high temperature even after it is irradiated with an ultraviolet ray.In the descriptions herein, the characteristics of the composition suchas the optical anisotropy and so forth are values measured in themethods disclosed in Examples. The content (percentage) of a liquidcrystal compound in a composition means the percentage by weight (% byweight) based on the total weight of liquid crystal compounds.

An advantage of the invention is to provide a liquid crystal compositionthat satisfies many characteristics among the characteristics such as ahigh maximum temperature of a nematic phase, a low minimum temperatureof a nematic phase, a small viscosity, a suitable optical anisotropy, anegatively large dielectric anisotropy, a small frequency dependency ofa dielectric anisotropy, a small temperature dependency of a thresholdvoltage and a large specific resistance. One aspect of the invention isto provide, for example, a liquid crystal composition properly balancedregarding many characteristics. Another aspect of the invention is toprovide a liquid crystal display device, for example, containing such acomposition and having a large voltage holding ratio. A further aspectof the invention is to provide an AM device, for example, containing acomposition with a minimum temperature of a nematic phase ofapproximately −30° C. or less, a maximum temperature of a nematic phaseof approximately 100° C. or more, a small viscosity, an opticalanisotropy ranging from approximately 0.05 to approximately 0.11 and adielectric anisotropy ranging from approximately −6.5 to approximately−2.0, and being suitable, for example, for a VA mode, an IPS mode and soforth.

The invention relates to a liquid crystal composition having a negativedielectric anisotropy and containing at least one compound selected froma group of compounds represented by formula (1) as a first component, atleast one compound selected from a group of compounds represented byformula (2) as a second component, at least one compound selected from agroup of compounds represented by formula (3) as a third component, andat least one compound selected from a group of compounds represented byformula (4) as a fourth component:

wherein the liquid crystal composition consists essentially of the firstcomponent, the second component, the third component and the fourthcomponent and wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³is alkyl or alkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or1,4-phenylene; A² is 1,4-cyclohexylene, 1,4-phenylene or2-fluoro-1,4-phenhlene; and Z¹ is a single bond or —COO—.

The invention also relates to a liquid crystal display device containingthe composition.

The liquid crystal composition of the invention satisfies manycharacteristics among the characteristics such as a high maximumtemperature of a nematic phase, a low minimum temperature of a nematicphase, a small viscosity, a suitable optical anisotropy, a negativelylarge dielectric anisotropy, a small frequency dependency of adielectric anisotropy, a small temperature dependency of a thresholdvoltage and a large specific resistance. The composition is, forexample, properly balanced regarding many characteristics. The devicecontains such a composition. The invention further includes a devicecontaining a composition, for example, with a minimum temperature of anematic phase of approximately −30° C. or less, a maximum temperature ofa nematic phase of approximately 100° C. or more, a small viscosity, anoptical anisotropy ranging from approximately 0.05 to approximately 0.11and a dielectric anisotropy ranging from approximately −6.5 toapproximately −2.0 has a large voltage holding ratio and is suitable,for example, for a VA mode, an IPS mode and so forth.

The invention includes:

1. A liquid crystal composition having a negative dielectric anisotropyand containing at least one compound selected from a group of compoundsrepresented by formula (1) as a first component, at least one compoundselected from a group of compounds represented by formula (2) as asecond component, at least one compound selected from a group ofcompounds represented by formula (3) as a third component, and at leastone compound selected from a group of compounds represented by formula(4) as a fourth component,

wherein the liquid crystal composition consists essentially of the firstcomponent, the second component, the third component and the fourthcomponent and wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³is alkyl or alkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or1,4-phenylene; A² is 1,4-cyclohexylene, 1,4-phenylene or2-fluoro-1,4-phenhlene; and Z¹ is a single bond or —COO—.

2. The liquid crystal composition according to item 1, wherein the ratioof the first component is in the range of from approximately 20% toapproximately 50% by weight, the ratio of the second component is in therange of from approximately 15% to approximately 40% by weight, theratio of the third component is in the range of from approximately 5% toapproximately 35% by weight and the ratio of the fourth component is inthe range of from approximately 5% to approximately 30% by weight, basedon the total weight of the liquid crystal compounds.

3. A liquid crystal composition having a negative dielectric anisotropyand comprising at least one compound selected from a group of compoundsrepresented by formula (1-2) as a first component, at least one compoundselected from a group of compounds represented by formulas (2-1) and(2-2) as a second component, at least one compound selected from a groupof compounds represented by formulas (3-1) to (3-3) as a third componentand at least one compound selected from a group of compounds representedby formula (4-1) as a fourth component:

wherein the liquid crystal composition consists essentially of the firstcomponent, the second component, the third component and the fourthcomponent and wherein R⁴ and R⁵ are independently alkyl; and R⁶ isalkenyl.

4. The liquid crystal composition according to item 3, wherein thesecond component is at least one compound selected from a group ofcompounds represented by formula (2-2).

5. The liquid crystal composition according to item 3, wherein thesecond component is at least one compound selected from a group ofcompounds represented by formula (2-1) and at least one compoundselected from a group of compounds represented by formula (2-2).

6. The liquid crystal composition according to any one of items 3 to 5,wherein the ratio of the first component is in the range of fromapproximately 20% to approximately 50% by weight, the ratio of thesecond component is in the range of from approximately 15% toapproximately 40% by weight, the ratio of the third component is in therange of from approximately 5% to approximately 35% by weight and theratio of the fourth component is in the range of from approximately 5%to approximately 30% by weight, based on the total weight of the liquidcrystal compounds.

7. The liquid crystal composition according to any one of items 1 to 6,wherein the composition further comprises an antioxidant.

8. The liquid crystal composition according to item 7, wherein theantioxidant is a compound represented by formula (8):

wherein m is an integer from 1 to 9.

9. The liquid crystal composition according to any one of items 7 or 8,wherein the ratio of the antioxidant is in the range of fromapproximately 50 ppm to approximately 600 ppm based on the total weightof the liquid crystal compounds.

10. A liquid display device comprising the liquid crystal compositionaccording to any one of items 1 to 9.

11. The liquid crystal composition according to item 1, wherein thecomposition contains only one of the first component and the secondcomponent.

In other words, the composition of item 11 has a negative dielectricanisotropy and contains at least one compound selected from a group ofcompounds represented by formulas (1) and (2), at least one compoundselected from a group of compounds represented by formula (3), and atleast one compound selected from a group of compounds represented byformula (4):

wherein the liquid crystal composition consists essentially of thesecompounds and wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³is alkyl or alkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or1,4-phenylene; A² is 1,4-cyclohexylene, 1,4-phenylene or2-fluoro-1,4-phenhlene; and Z¹ is a single bond or —COO—.

12. The liquid crystal composition according to item 1, wherein theratio of the group of compounds represented by formulas (1) and (2) isin the range of from approximately 35% to approximately 90% by weight,the ratio of the group of compounds represented by formula (3) is in therange of from approximately 5% to approximately 35% by weight and theratio of the group of compounds represented by formula (4) is in therange of from approximately 5% to approximately 30% by weight, based onthe total weight of the liquid crystal compounds.

13. The liquid crystal composition according to any one of items 111 and12, wherein the composition further contains an antioxidant.

14. The liquid crystal composition according to item 13, wherein theantioxidant is a compound represented by formula (8):

wherein m is an integer from 1 to 9.

15. The liquid crystal composition according to any one of items 13 or14, wherein the ratio of the antioxidant is in the range of fromapproximately 50 ppm to approximately 600 ppm based on the total weightof the liquid crystal compounds.

16. A liquid display device containing the liquid crystal compositionaccording to any one of items 11 to 15.

The invention further includes: (1) The composition described above,wherein the optical anisotropy is in the range from approximately 0.05to approximately 0.11; (2) The composition described above, wherein themaximum temperature of the nematic phase is approximately 100° C. ormore and the minimum temperature of the nematic phase is approximately−30° C. or less; (3) The composition described above, which furtherincludes an optically active compound; (4) An AM device containing thecomposition described above; (5) A device containing the compositiondescribed above and having the mode of IPS or VA; (6) A device of atransmission type, containing the composition described above; (7) Anamorphous silicon or polycrystalline silicon TFT device, containing thecomposition described above; (8) Use of the composition described aboveas a composition having a nematic phase; and (9) Use as an opticallyactive composition by adding an optically active compound to thecomposition described above.

The composition of the invention will be explained in the followingorder. First, the main characteristics of the component compounds andthe main effects of the compounds on the composition will be explained.Second, a desirable ratio of the component compounds and the basisthereof will be explained. Third, a desirable embodiment of thecomponent compounds will be explained. Fourth, examples of the componentcompound will be shown. Fifth, the preparation methods of the componentcompound will be explained. Lastly, use of the composition will beexplained.

First, the main characteristics of the component compounds and the maineffects of the compounds on the composition will be explained. The maincharacteristics of the component compounds are summarized in Table 2. InTable 2, the letter L represents large or high, the letter M representsa middle degree and the letter S represents small or low. The numeral 0(zero) indicates that a dielectric anisotropy is nearly zero (or verysmall in value). TABLE 2 Characteristics of Compounds (1) (2) (3) (4)Maximum Temperature S M S L Viscosity M M S M Optical Anisotropy S M SM-L Dielectric Anisotropy M-L M-L 0 0 (negatively (negatively largevalues) large values) Specific Resistance L L L L

The specific feature of the composition lies in the combination of thecompounds (1) to (4). The compound (1) and the compound (2) have a largeeffect for increasing negatively a dielectric anisotropy of thecomposition. The compound (3) has a large effect for decreasing aviscosity of the composition. The compound (4) has a large effect forincreasing a maximum temperature of the composition. Dielectricanisotropy of the typical component compounds is summarized in Table 3.Table 3 illustrates that a low threshold voltage for driving a devicedepends mainly on the compound (1) and the compound (2). The compoundsare shown according to the notation in Table 4. TABLE 3 DielectricAnisotropy of Compounds Compound No. Compound Dielectric anisotropy(1-2) 3-HB(2F,3F)-O2 −6.0 (2-1) 2-HHB(2F,3F)-1 −3.6 (2-2)5-HHB(2F,3F)-O2 −5.9 (3-1) 3-HH-4 0.3 (3-2) 3-HH-O1 −0.2 (3-3) 5-HH-V0.3 (4-1) 3-HHEBH-5 −0.8

The main effects of the compounds on the composition will be explained.The compound (1) decreases a maximum temperature of a nematic phase,increases negatively a dielectric anisotropy, and increases a viscosityof the composition. The compound (2) increases a maximum temperature ofa nematic phase, increase negatively a dielectric anisotropy, andincreases a viscosity of the composition. The compound (3) decreases amaximum temperature of a nematic phase, makes a dielectric anisotropyclose to zero, and decreases a viscosity of the composition. Thecompound (4) increases particularly a maximum temperature of a nematicphase of the composition, and makes the dielectric anisotropy of thecomposition close to zero.

The compound (1) includes compounds (1-1) to (1-4). The compounds (1-2)and (1-4) particularly increase negatively a dielectric anisotropy ofthe composition. The compound (2) includes compounds (2-1) to (2-4). Thecompounds (2-1) and (2-3) particularly decrease a minimum temperature ofa nematic phase of the composition. The compound (2-2) and (2-4)particularly increase negatively a dielectric anisotropy of thecomposition. The compound (3) includes compounds (3-1) to (3-5). Thecompound (3-1) particularly decreases a viscosity of the composition.The compound (3-2) particularly decreases a minimum temperature of anematic phase of the composition. The compound (3-3) decreases a minimumtemperature of a nematic phase and simultaneously decreases a viscosityof the composition. The compound (4) includes compounds (4-1) to (4-4).The compound (4-1) increases a maximum temperature of a nematic phaseand simultaneously decreases an optical anisotropy of the composition.

Second, a desirable ratio of the component compounds and the basistherefor will be explained. A desirable ratio of the first component isapproximately 20% by weight or more for increasing negatively adielectric anisotropy and is approximately 50% by weight or less forincreasing a maximum temperature. A more desirable ratio is fromapproximately 25% to approximately 40% by weight for further increasingnegatively a dielectric anisotropy and further increasing a maximumtemperature.

A desirable ratio of the second component is approximately 15% by weightor more for increasing a maximum temperature and is approximately 40% byweight or less for decreasing a minimum temperature. A more desirableratio is from approximately 20% to approximately 35% by weight forfurther increasing a maximum temperature and further decreasing aminimum temperature.

A desirable ratio of the third component is approximately 5% by weightor more for decreasing a viscosity and is approximately 35% by weight orless for increasing negatively a dielectric anisotropy. A more desirableratio is from approximately 15% to approximately 30% by weight forfurther decreasing a viscosity and further increasing negatively adielectric anisotropy.

A desirable ratio of the fourth component is approximately 5% by weightor more for increasing a maximum temperature and is approximately 30% byweight or less for decreasing a minimum temperature. A more desirableratio is from approximately 10% to approximately 25% by weight forfurther increasing a maximum temperature and further decreasing aminimum temperature.

Only one of the first component and the second component may be used asa component compound. In this case, a desirable ratio of the firstcomponent or the second component is approximately 35% by weight or morefor increasing negatively a dielectric anisotropy and is approximately90% by weight or less for decreasing a viscosity. A more desirable ratiois from approximately 45% to approximately 75% by weight for furtherincreasing negatively a dielectric anisotropy and further decreasing aviscosity.

Third, a desirable embodiment of the component compound will beexplained. The symbol R¹ was used for many compounds in the chemicalformulas for the component compounds. R¹ may be identical or differentin these compounds. In one case, for example, R¹ of the compound (1) isethyl and R¹ of the compound (2) is ethyl. In another case, R¹ of thecompound (1) is ethyl and R¹ of the compound (2) is propyl. This rule isalso applicable to the symbols R², A¹, Z¹, X¹, Y¹, and so forth.

Desirable R¹ is alkyl having 1 to 10 carbons or alkenyl having 2 to 10carbons. Desirable R² is alkyl having 1 to 10 carbons or alkoxy having 1to 10 carbons. Desirable R³ is alkyl having 1 to 10 carbons oralkoxymethyl having 2 to 10 carbons. Desirable R⁴ and R⁵ are alkylhaving 1 to 10 carbons. Desirable R⁶ is alkenyl having 2 to 10 carbons.

Desirable alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,or octyl. More desirable alkyl is ethyl, propyl, butyl, pentyl, orheptyl for decreasing a viscosity.

Desirable alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy, or heptyloxy. More desirable alkoxy is methoxy or ethoxy fordecreasing a viscosity.

Desirable alkoxymethyl is methoxymethyl, ethoxymethyl, propoxymethyl,butoxymethyl, or pentyloxymethyl. More desirable alkoxymethyl ismethoxymethyl for decreasing a viscosity.

Desirable alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, or 5-hexenyl. More desirablealkenyl is vinyl, 1-propenyl, 3-butenyl, or 3-pentenyl, for example, fordecreasing a viscosity. A desirable configuration of —CH═CH— in thesealkenyl depends on the position of a double bond. Trans is desirable inthe alkenyl such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl,3-pentenyl, and 3-hexenyl, for example, for decreasing a viscosity. Cisis desirable in the alkenyl such as 2-butenyl, 2-pentenyl and 2-hexenyl,for example, for decreasing a viscosity.

In the alkyl, the alkoxy, the alkoxymethyl and the alkenyl, a linearform is desirable in view of a viscosity of the compound.

A¹ is 1,4-cyclohexylene or 1,4-phenylene. A² is 1,4-cyclohexylene,1,4-phenylene or 2-fluoro-1,4-phenylene. On the configuration of1,4-cyclohexylene, trans is preferable to cis in consideration of aliquid crystal phase of the compound. Fluorine of2-fuluoro-1,4-phenylene is positioned on the right side or the left sideof the ring. A desirable position is the right side as in the compound(4-4).

Z¹ is a single bond or —COO—. A bonding group of —COO— is positioned inthe direction in the compound (4-1).

Fourth, examples of the component compound will be shown. In thedesirable compounds described below, R⁴ and R⁵ are independently alkylhaving 1 to 10 carbons, and R⁶ is alkenyl having 2 to 10 carbons. Moredesirable alkyl or alkenyl is as described above. In these desirablecompounds, trans is preferable to cis for the configuration of1,4-cyclohexylene in consideration of a liquid crystal phase of thecompound.

Desirable compound (1) is the compounds (1-1) to (1-4). More desirablecompound (1) is the compound (1-1) for decreasing a production cost.Particularly desirable compound (1) is the compound (1-2) forparticularly increasing negatively a dielectric anisotropy of thecomposition.

Desirable compound (2) is the compounds (2-1) to (2-4). More desirablecompound (2) is the compounds (2-1) and (2-2) for decreasing aproduction cost. The compound (2-1) is particularly desirable fordecreasing a viscosity of the composition. The compound (2-2) isparticularly desirable for increasing negatively a dielectric anisotropyof the composition.

Desirable compound (3) is the compounds (3-1) to (3-5). More desirablecompound (3) is the compounds (3-1) to (3-3) and (3-5) for decreasing aminimum temperature of the composition. Particularly desirable compound(3) is the compounds (3-1) to (3-3) for further decreasing a viscosityof the composition.

Desirable compound (4) is the compounds (4-1) to (4-4). More desirablecompound (4) is the compounds (4-1), (4-3) and (4-4) for decreasing aminimum temperature of the composition. Particularly desirable compound(4) is the compound (4-1) for further decreasing a viscosity of thecomposition.

When an optically active compound is added to the composition, adesirable optically active compound is compounds represented by formulas(7-1) to (7-4).

When an antioxidant is added to the composition, a desirable antioxidantis the compound (8):

wherein m is an integer from 1 to 9. Desirable m is 1, 3, 5, 7, or 9.More desirable m is 1 and 7. When m is 1, the compound has a largevolatility, and is effective in preventing the decrease of specificresistance caused by heating in the air. When m is 7, the compound has asmall volatility, and is effective in maintaining a large voltageholding ratio at room temperature and also at a high temperature evenafter the device has been used for a long time.

Fifth, the preparation methods of the component compounds will beexplained. These compounds can be prepared by known methods. Thepreparation method will be exemplified below. The compounds (1-2), (2-1)and (2-2) are prepared by the method disclosed in JP H2-503441 A/1990.The compound (3-1) is prepared by the method disclosed in JP S59-70624A/1984. The compound (4-3) is prepared by the method disclosed in JPS58-219137A/1983. The compound (8), wherein m is 1, is commerciallyavailable. The compound is available, for example, from Sigma-Aldrich,Inc. The compound (8), wherein m is 7, is prepared by the methoddisclosed in U.S. Pat. No. 3,660,505.

The compounds for which preparation methods were not described above canbe prepared according to the methods described in ORGANIC SYNTHESES(John Wiley & Sons, Inc.), ORGANIC REACTIONS (John Wiley & Sons, Inc.),COMPREHENSIVE ORGANIC SYNTHESIS (Pergamon Press), NEW EXPERIMENTALCHEMISTRY COURSE (Shin Jikken Kagaku Kouza) (Maruzen, Inc.), and soforth. The composition is prepared according to known methods using thecompounds thus obtained. For example, the component compounds are mixedand dissolved in each other by heating.

Lastly, use of the composition will be explained. Most of thecompositions have a minimum temperature of approximately −30° C. orless, a maximum temperature of 100° C. or more, a dielectric anisotropyof approximately −6.5 to approximately −2.0, and an optical anisotropyof approximately 0.05 to approximately 0.11. The composition having anoptical anisotropy of approximately 0.05 to approximately 0.18 andfurther the composition having an optical anisotropy of approximately0.05 to approximately 0.20 may be prepared by controlling ratios of thecomponent compounds. The composition can be used as a composition havinga nematic phase and as an optically active composition by adding anoptically active compound.

The composition can be used for an AM device. It can also be used for aPM device. The composition can also be used for an device having a modesuch as PC, TN, STN, ECB, OCB, IPS, and so forth. It is particularlydesirable to use the composition for a device having a mode of VA orIPS. These devices may be of a reflection type, a transmission type or asemi-transmission type. It is desirable to use the composition for adevice of a transmission type. It can be used for an amorphoussilicon-TFT device or a polycrystal silicon-TFT device. The compositionis also usable for a nematic curvilinear aligned phase (NCAP) deviceprepared by microcapsulating the composition, and for a polymerdispersed (PD) device in which a three dimensional net-work polymer isformed in the composition, for example, a polymer network (PN) device.

SPECIFIC EXAMPLES

The following examples are for illustrative purposes only and are notintended, nor should they be interpreted to, limit the scope of theinvention.

The invention will be explained in detail by way of Examples. Theinvention is not limited by the Examples described below. The compoundsdescribed in the Comparative Examples and the Examples are expressed bythe symbols according to the definition in Table 4 below. Theparenthesized number next to the symbolized compounds in the Examplescorresponds to the number of the desirable compound. A ratio(percentage) of a liquid crystal compound is percentage by weight (% byweight) based on the total weight of liquid crystal compounds. Lastly,the characteristics of the composition are summarized. TABLE 4 Method ofDescription of Compound using Symbols R—(A₁)—Z₁—. . .—Z_(n)—(A_(n))—XSymbol 1) Left Terminal Group R— C_(n)H_(2n+1)— n— C_(n)H_(2n+1)O— nO—C_(n)H_(2n+1)OC_(m)H_(2m)— nOm— CH₂═CH— V— CH₂═CHC_(n)H_(2n)— Vn—CF₂═CH— VFF— 2) Ring Structure —An—

B

B(2F)

B(F)

B(2F,3F)

H 3) Bonding Group —Zn— —C₂H₄— 2 —COO— E —CH₂O— 10 4) Right TerminalGroup —X —C_(n)H_(2n+1) —n —OC_(n)H_(2n+1) —On —CH═CH₂ —V—CH═CHC_(n)H_(2n+1) —Vn —Cl —CL 5) Example of Description Example 13-HHB(2F,3F)-O2

Example 2 101-HBBH-5

Example 3 5-HH-V

The composition is prepared by first measuring components such as aliquid crystal compound and then by mixing them. Thus, it is easy tocalculate the percentage by weight of the component. However, it is noteasy to calculate exactly the ratios of the components by analyzing thecomposition with gas chromatography. It is because the correctioncoefficient depends on the kind of a liquid crystal compound.Fortunately, the correction coefficient is approximately 1. Furthermore,the difference of approximately 1% by weight only slightly influences oncharacteristics of the composition. Therefore, the peak area ratio ofthe component peaks in the gas chromatograph can be regarded as apercentage by weight of the component compound. Namely, the results ofgas chromatographic analysis (peak area ratio) are considered to beequivalent to the percentage by weight of a liquid crystal compoundwithout correction.

When a sample was a composition, it was measured as it was, and theobtained value is described here. When a sample was a compound, a samplefor measurement was prepared by mixing 15% by weight of the compound and85% by weight of mother liquid crystals. A value of characteristic ofthe compound was calculated by extrapolating from a value obtained bymeasurement. Namely: extrapolated value=(value measured−0.85×valuemeasured for mother liquid crystals)/0.15. When a smectic phase (orcrystals) separated out at this ratio at 25° C., a ratio of the compoundand mother liquid crystals was changed step by step in the order of (10%by weight/90% by weight), (5% by weight/95% by weight), (1% byweight/99% by weight), respectively. Values for a maximum temperature,optical anisotropy, viscosity, and dielectric anisotropy of the compoundwere obtained by the extrapolation.

The composition of the mother liquid crystals is as shown below.

Measurement of the characteristics was carried out according to thefollowing methods. Most methods are described in the Standard ofElectric Industries Association of Japan, EIAJ ED-2521 A or those withsome modifications. A TFT was not attached to TN and VA devices used formeasurement.

A maximum temperature of a nematic phase (NI; ° C.): A sample was placedon a hot plate in a melting point apparatus equipped with a polarizingmicroscope and was heated at the rate of 1° C. per minute. A temperaturewas measured when a part of the sample began to change from a nematicphase into an isotropic liquid. A higher limit of a temperature range ofa nematic phase may be abbreviated to “a maximum temperature.”

A minimum temperature of a nematic phase (Tc; ° C.): A sample having anematic phase was put in a VA device having a distance between two glasssubstrates (cell gap) of 4 micrometers with an antiparallel rubbingdirection, and the device was sealed with an UV curable adhesive. Thedevice was then kept in a freezer at temperatures of 0° C., −10° C.,−20° C., and −30° C. for ten days, respectively, and a liquid crystalphase was observed. For example, when the sample remained in a nematicphase at −20° C. and changed to crystals (or a smectic phase) at −30°C., Tc was expressed as ≦−20° C. A lower limit of a temperature range ofa nematic phase may be abbreviated to “a minimum temperature.”

Optical anisotropy (Δn; measured at 25° C.): Measurement was carried outwith an Abbe refractometer mounting a polarizing plate on an ocularusing a light at a wavelength of 589 nanometers. The surface of a mainprism was rubbed in one direction, and then a sample was dropped on themain prism. Refractive index n∥ was measured when the direction of apolarized light was parallel to that of the rubbing. Refractive index n⊥was measured when the direction of a polarized light was perpendicularto that of the rubbing. A value of optical anisotropy was calculatedfrom the equation: Δn=n∥−n™.

Dielectric anisotropy (Δε; measured at 25° C.): A sample having anematic phase was put in a VA device having a distance between two glasssubstrates (cell gap) of 4 micrometers with an antiparallel rubbingdirection, and the device was sealed with an UV curable adhesive. Sinewaves (10 volts, 1 kilohertz) were impressed onto the device, and adielectric constant (ε∥) that is parallel to a liquid crystal moleculewas measured after 2 seconds. A sample was put in a TN device having adistance between two glass substrates (all gap) of a micrometers and atwist angle of 80°. Sine waves (0.5 volts, 1 kilohertz) were impressedonto the device, and a dielectric constant (ε⊥) that is perpendicular toa liquid crystal molecule was measured after 2 seconds. A value of adielectric anisotropy was calculated from the equation; Δε=ε∥−ε⊥.

Frequency dependency of dielectric anisotropy (Δε−f; measured at −20°C.): Dielectric anisotropy at −20° C. was measured by the measurementmethod for dielectric anisotropy described above. The frequency of thesine wave was 100 Hz and 100 kHz, and ε∥ or ε⊥ was measured after 6seconds from impressing a voltage. Frequency dependency of dielectricanisotropy was a value obtained by subtracting a dielectric anisotropymeasured at 100 kHz from a dielectric anisotropy measured at 100 Hz. Itwas determined that when the value was as close as to zero, frequencydependency of dielectric anisotropy was small. That is, the sample wasexcellent in frequency dependency of dielectric anisotropy. Frequencydependency of dielectric anisotropy may be abbreviated to “frequencydependency.”

Threshold voltage (Vth; measured at 25° C.; V): Measurements werecarried out with LCD Evaluation System Model LCD-5100 made by OtsukaElectronics Co., Ltd. Light source is a halogen lamp. A sample waspoured into a VA device of a normally black mode, in which a cell gapbetween two glass plates was 4 micrometers with an antiparallel rubbingdirection, and the device was sealed with an UV curable adhesive.Voltage to be impressed onto the device (70 Hz, rectangular waves) wasstepwise increased by 0.02 volt starting from zero volt up to 20 volts.During the stepwise increasing, a light was irradiated to the device ina perpendicular direction, and an amount of the light passing throughthe device was measured. Voltage-transmission curve was prepared, inwhich a maximum amount of a light corresponded to 100% transmittance, aminimum amount of a light corresponded to 0% transmittance. Thresholdvoltage is a value at 10% transmittance.

Temperature dependency of threshold voltage (Vth-T; V): Thresholdvoltage was measured at 20° C. and 70° C. by the measurement method forthreshold voltage described above. Temperature dependency of thresholdvoltage was a value obtained by subtracting a threshold voltage measuredat 70° C. from a threshold voltage measured at 20° C. It was determinedthat when the value was as close as to zero, temperature dependency ofthreshold voltage was small, that is, the sample was excellent intemperature dependency of threshold voltage. Temperature dependency ofthreshold voltage may be abbreviated to “temperature dependency.”

Voltage holding ratio (VHR; measured at 25° C. and 100° C.; %): A TNdevice used for measurement has a polyimide-alignment film and the cellgap between two glass plates is 4.5 micrometers. A sample was pouredinto the device, and then the device was sealed with an adhesive whichis polymerized by the irradiation of ultraviolet light. The TN devicewas impressed and charged with pulse voltage (60 microseconds at 5volts). Decreasing voltage was measured for 16.7 milliseconds with HighSpeed Voltmeter and the area A between a voltage curve and a horizontalaxis in a unit cycle was obtained. The area B was an area withoutdecreasing. Voltage holding ratio is a percentage of the area A to thearea B. A voltage holding ratio obtained at 25° C. was expressed asVHR-1. A voltage holding ratio obtained at 100° C. was expressed asVHR-2. Next, this TN device was heated at 100° C. for 250 hours.Separately, this TN device was irradiated with an ultraviolet ray (UV).The irradiation condition was a high-pressure mercury lamp (USH-500D,produced by Ushio, Inc., 500 W) as an UV light source, a distancebetween the light source and the device of 20 cm, and an irradiationtime of 20 minutes. VHR-3 is a voltage holding ratio measured at 25° C.after heating. VHR-4 is a voltage holding ratio measured at 100° C.after heating. VHR-5 is a voltage holding ratio measured at 25° C. afterirradiation with UV. VHR-6 is a voltage holding ratio measured at 100°C. after irradiation with UV. VHR-1 and VHR-2 correspond to evaluationof a device at the initial stage. VHR-3 and VHR-4 correspond toevaluation of a device after it has been used for a long time. VHR-5 andVHR-6 correspond to evaluation of light stability of a device.

Response time (τ; measured at 25° C.; millisecond): Measurement wascarried out with LCD Evaluation System Model LCD-5100 made by OtsukaElectronics Co., Ltd. Light source is a halogen lamp. Low-pass filterwas set at 5 kilohertz. A sample was poured into a VA device of anormally black mode, in which a cell gap between two glass plates was 4micrometers with an antiparallel rubbing direction, and the device wassealed with an UV curable adhesive. Rectangle waves (70 Hertz, a voltagewhere a transmission of 100% was obtained in the measurement ofthreshold voltage, 0.5 seconds) was impressed to the device. Duringimpressing, a light was irradiated to the device in a perpendiculardirection, and an amount of the light passing through the device wasmeasured. A maximum amount of a light corresponds to 100% transmittance,and a minimum amount of a light corresponds to 0% transmission. Falltime (τf) is a period of time required for the change in transmittancefrom 100% to 0%. Response time is the fall time.

Rotation viscosity (γ1; measured at 25° C.; mPa·s): Rotation viscositywas measured according to the method disclosed in M. Imai, et al.,Molecular Crystals and Liquid Crystals, Vol. 259, p. 37 (1995). A samplewas placed in VA device of a normally black mode, in which a cell gapbetween two glass plates was 4 micrometers with an antiparallel rubbingdirection, and the device was sealed with an UV curable adhesive. The VAdevice was impressed with a voltage in a range of from 10 V to 20 Vstepwise by 1 V. After a period of 0.2 second with no impress ofvoltage, voltage impress was repeated with only one rectangular wave(rectangular pulse of 0.2 second) and application of no voltage (2seconds). A peak current and a peak time of a transient currentgenerated by the voltage impress were measured. Rotation viscosity wasobtained from the measured values and the calculating equation (8) inthe literature by M. Imai, et al. As the dielectric anisotropy necessaryfor the calculation, the value measured by the measuring method ofdielectric anisotropy described above was used.

Gas chromatographic Analysis: Gas Chromatograph Model GC-14B made byShimadzu was used for measurement. Carrier gas is helium (2 millilitersper minute). An evaporator and a detector (FID) were set up at 280° C.and 300° C., respectively. Capillary column DB-1 (length 30 meters, bore0.32 millimeters, film thickness 0.25 micrometers, dimethylpolysiloxaneas stationary phase, no polarity) made by Agilent Technologies, Inc. wasused for the separation of the component compound. After the column hadbeen kept at 200° C. for 2 minutes, it was further heated to 280° C. atthe rate of 5° C. per minute. A sample was prepared into an acetonesolution (0.1% by weight), and 1 microliter of the solution was injectedinto the evaporator. The recorder used was Chromatopac Model C-R5A madeby Shimadzu or its equivalent. Gas chromatogram obtained showed aretention time of a peak and a peak area corresponding to the componentcompound.

Solvents for diluting the sample may also be chloroform, hexane, and soforth. The following capillary columns may also be used: HP-1 made byAgilent Technologies Inc. (length 30 meters, bore 0.32 millimeters, filmthickness 0.25 micrometers), Rtx-1 made by Restek Corporation (length 30meters, bore 0.32 millimeters, film thickness 0.25 micrometers), andBP-1 made by SGE International Pty. Ltd. (length 30 meters, bore 0.32millimeters, film thickness 0.25 micrometers). In order to preventcompound peaks from overlapping, a capillary column CBP1-M50-025 (length50 meters, bore 0.25 millimeters, film thickness 0.25 micrometers) madeby Shimadzu Corporation may be used. An area ratio of each peak in thegas chromatogram corresponds to a ratio of the component compound.Percentage by weight of the component compound is not completelyidentical to an area ratio of each peak. According to the invention,however, percentage by weight of the component compound may be regardedto be identical to an area ratio of each peak, when these capillarycolumns are used. This is because there is no significant difference incorrection efficient of component compounds.

Comparative Example 1

Example 1 was chosen from the compositions disclosed in JP H10-176167A/1998. The basis is that the composition contains the compound (1), thecompound (2) and the compound (3) of the invention, and has the highestmaximum temperature. The components and characteristics of thecomposition are as follows. The composition has a low maximumtemperature and a large temperature dependency of threshold voltage.3-HB(2F,3F)-O2 (1-2) 12%  5-HB(2F,3F)-O2 (1-2) 11%  3-HHB(2F,3F)-O2(2-2) 15%  5-HHB(2F,3F)-O2 (2-2) 15%  3-HH-4 (3-1) 5% 3-HH-5 (3-1) 5%3-HH-O1 (3-2) 6% 3-HH-O3 (3-2) 6% 3-HB-2 (3-4) 4% 3-HB-O1 (3-5) 4%3-HHEH-3 (—) 5% 3-HHEH-5 (—) 6% 4-HHEH-3 (—) 6%

NI=91.3° C.; T_(C)≦−30° C.; Δn=0.076; Δε=−3.2; Vth-T=0.16 V;VHR-1=99.0%.

Comparative Example 2

Example 4 was chosen from the compositions disclosed in JP 2000-96055A/2000. The basis is that the composition contains the compound (1), thecompound (2), the compound (3) and the compound (4) of the invention.The components and characteristics of the composition are as follows.The composition has a low maximum temperature, a negatively smalldielectric anisotropy and a large temperature dependency of thresholdvoltage. 5-HB(2F,3F)-O2 (1-2) 14% 2-HHB(2F,3F)-1 (2-1) 6.5% 3-HHB(2F,3F)-O2 (2-2) 14% 5-HHB(2F,3F)-O2 (2-2) 14% 3-HHEB(2F,3F)-O2 (—) 6% 3-HH-4 (3-1)  5% 3-HH-5 (3-1)  5% 3-HH-O1 (3-2) 10% 5-HH-O1 (3-2) 9% 5-HH-V (3-3) 4.5%  5-HB-3 (3-4) 10% 3-HHEBH-5 (4-1)  2%

NI=85.1° C.; T_(C)≦−30° C.; Δn=0.072; Δε=−2.5; Vth-T=0.30 V;VHR-1=99.1%.

Comparative Example 3

Example 7 was chosen from the compositions disclosed in JP 2001-354967A/2001. The basis is that the composition contains the compound (1), thecompound (2), the compound (3) and the compound (4) of the invention,and has the highest maximum temperature. The components andcharacteristics of the composition are as follows. The composition has alow maximum temperature and a large temperature dependency of thresholdvoltage. 3-HB(2F,3F)-O4 (1-2) 14% 5-HB(2F,3F)-O2 (1-2)  7%5-HB(2F,3F)-O4 (1-2) 18% 3-HHB(2F,3F)-O2 (2-2) 13% 2-HBB(2F,3F)-O2 (—)12% 3-HBB(2F,3F)-O2 (—) 12% 3-HH-5 (3-1)  5% 3-HH-V1 (3-3)  8% 5-HH-V(3-3)  8% 3-HHEBH-3 (4-1)  3%

NI=80.6° C.; T_(C)≦−30° C.; Δn=0.101; Δε=−4.4; Vth-T=0.27 V;VHR-1=99.0%.

Comparative Example 4

Example 16 was chosen from the compositions disclosed in JP 2003-13065A/2003. The basis is that the composition contains the compound (1), thecompound (2) and the compound (3) of the invention, and has the highestmaximum temperature. The components and characteristics of thecomposition are as follows. The composition has a low maximumtemperature, a negatively small dielectric anisotropy and a largetemperature dependency of threshold voltage. 3-HB(2F,3F)-O4 (1-2) 4%5-HB(2F,3F)-O2 (1-2) 12%  5-HB(2F,3F)-O4 (1-2) 9% 1-HHB(2F,3F)-O2 (2-2)12%  2-HBB(2F,3F)-O2 (—) 13%  3-HBB(2F,3F)-O2 (—) 13%  3-HH-5 (3-1) 6%3-HH-V1 (3-3) 11%  5-HH-V (3-3) 12%  3-HH1OH-3 (—) 3% 4-HH1OH-3 (—) 3%3-HBB-2 (—) 2%

NI=86.0° C.; T_(C)≦−30° C.; Δn=0.097; Δε=−3.2; Vth-T=0.16 V;VHR-1=98.9%.

Example 1

3-HB(2F,3F)-O2 (1-2) 18% 5-HB(2F,3F)-O2 (1-2) 18% 3-HHB(2F,3F)-O2 (2-2)12% 5-HHB(2F,3F)-O2 (2-2) 12% 3-HH-4 (3-1)  5% 3-HH-O1 (3-2)  7% 5-HH-V(3-3)  5% 3-HB-O2 (3-5)  3% 3-HHEBH-3 (4-1) 10% 3-HHEBH-5 (4-1) 10%

NI=106.5° C.; T_(C)≦−30° C.; Δn=0.086; Δε=−3.4; γ1=64.3 mPa·s;Vth-T=0.09 V; Δε-f=−0.53; VHR-1=99.2%.

Example 2

5-HB(2F,3F)-1 (1-1) 3% 3-HB(2F,3F)-O2 (1-2) 16%  5-HB(2F,3F)-O2 (1-2)17%  3-HHB(2F,3F)-1 (2-1) 3% 3-HHB(2F,3F)-O2 (2-2) 11%  5-HHB(2F,3F)-O2(2-2) 11%  3-HH-O1 (3-2) 7% 5-HH-V (3-3) 10%  5-HB-3 (3-4) 3% 3-HHEBH-3(4-1) 7% 3-HHEBH-5 (4-1) 7% 1O1-HBBH-5 (4-3) 5%

NI=100.5° C.; T_(C)≦−30° C.; Δn=0.087; Δε=−3.3; Δ1=84.6 mPa·s;Vth-T=0.06 V; Δε-f=−0.23; VHR-1=99.2%.

Example 3

3-HB(2F,3F)-O2 (1-2) 16%  5-HB(2F,3F)-O2 (1-2) 16%  V2-HB(2F,3F)-O2(1-4) 4% 3-HHB(2F,3F)-O2 (2-2) 10%  5-HHB(2F,3F)-O2 (2-2) 12% V2-HHB(2F,3F)-O2 (2-4) 4% 3-HH-4 (3-1) 5% 3-HH-V1 (3-3) 5% 5-HH-V (3-3)10%  3-HHEBH-3 (4-1) 9% 3-HHEBH-5 (4-1) 9%

NI=111.3° C.; T_(C)≦−30° C.; Δn=0.087; Δε=−3.6; γ1=89.5 mPa·s;Vth-T=0.08 V; Δε-f=−0.77; VHR-1=99.0%.

Example 4

3-HB(2F,3F)-O2 (1-2) 18%  5-HB(2F,3F)-O2 (1-2) 18%  3-HHB(2F,3F)-1 (2-1)3% 3-HHB(2F,3F)-O2 (2-2) 10%  5-HHB(2F,3F)-O2 (2-2) 10%  3-HH-4 (3-1) 5%3-HH-O1 (3-2) 11%  3-HB-O2 (3-5) 3% 3-HHEBH-3 (4-1) 9% 3-HHEBH-5 (4-1)9% 3-HB(F)BH-3 (4-4) 4%

NI=107.2° C.; T_(C)≦−30° C.; Δn=0.088; Δε=−3.5; γ1=93.9 mPa·s;Vth-T=0.07 V; Δε-f=−0.57; VHR-1=99.0%.

Example 5

3-HB(2F,3F)-O2 (1-2) 18% 5-HB(2F,3F)-O2 (1-2) 18% 3-HHB(2F,3F)-O2 (2-2)12% 5-HHB(2F,3F)-O2 (2-2) 12% 3-HH-4 (3-1)  5% 3-HH-O1 (3-2)  7% 5-HH-V(3-3)  5% 3-HB-O2 (3-5)  3% 3-HHEBH-3 (4-1) 10% 3-HHEBH-5 (4-1) 10%

An antioxidant of the compound (8) wherein m is 1 was added in an amountof 200 ppm to the above composition. The composition had the followingcharacteristics: NI=106.5° C.; T_(C)≦−30° C.; Δn=0.086; Δε=−3.4; γ1=64.3mPa·s; Vth-T=0.09 V; Δε-f=−0.53; VHR-1=99.2%.

Example 6

5-HB(2F,3F)-1 (1-1) 3% 3-HB(2F,3F)-O2 (1-2) 16%  5-HB(2F,3F)-O2 (1-2)17%  3-HHB(2F,3F)-1 (2-1) 3% 3-HHB(2F,3F)-O2 (2-2) 11%  5-HHB(2F,3F)-O2(2-2) 11%  3-HH-O1 (3-2) 7% 5-HH-V (3-3) 10%  5-HB-3 (3-4) 3% 3-HHEBH-3(4-1) 7% 3-HHEBH-5 (4-1) 7% 1O1-HBBH-5 (4-3) 5%

An antioxidant of the compound (8) wherein m is 7 was added in an amountof 300 ppm to the above composition. The composition had the followingcharacteristics: NI=100.5° C.; T_(C)≦−30° C.; Δn=0.087; Δε=−3.3; γ1=84.6mPa·s; Vth-T=0.06 V; Δε-f=−0.23; VHR-1=99.2%.

Although the invention has been described and illustrated with a certaindegree of particularity, it is understood that the present disclosurehas been made only by way of example, and that numerous changes in theconditions and order of steps can be resorted to by those skilled in theart without departing from the spirit and scope of the invention.

1. A liquid crystal composition having a negative dielectric anisotropyconsisting essentially of at least one compound selected from a group ofcompounds represented by formula (1) as a first component, at least onecompound selected from a group of compounds represented by formula (2)as a second component, at least one compound selected from a group ofcompounds represented by formula (3) as a third component and at leastone compound selected from a group of compounds represented by formula(4) as a fourth component:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl oralkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or 1,4-phenylene; A²is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenhlene; and Z¹ isa single bond or —COO—.
 2. The liquid crystal composition according toclaim 1, wherein the ratio of the first component is in a range of fromapproximately 20% to approximately 50% by weight, the ratio of thesecond component is in a range of from approximately 15% toapproximately 40% by weight, the ratio of the third component is in arange of from approximately 5% to approximately 35% by weight and theratio of the fourth component is in a range of from approximately 5% toapproximately 30% by weight, based on the total weight of the liquidcrystal compounds.
 3. A liquid crystal composition having a negativedielectric anisotropy consisting essentiall of at least one compoundselected from a group of compounds represented by formula (1-2) as thefirst component, at least one compound selected from a group ofcompounds represented by formulas (2-1) and (2-2) as the secondcomponent, at least one compound selected from a group of compoundsrepresented by formulas (3-1) to (3-3) as the third component and atleast one compound selected from a group of compounds represented byformula (4-1) as the fourth component:

wherein R⁴ and R⁵ are independently alkyl; and R⁶ is alkenyl.
 4. Theliquid crystal composition according to claim 3, wherein the secondcomponent is at least one compound selected from a group of compoundsrepresented by formula (2-2).
 5. The liquid crystal compositionaccording to claim 3, wherein the second component is at least onecompound selected from a group of compounds represented by formula (2-1)and at least one compound selected from a group of compounds representedby formula (2-2).
 6. The liquid crystal composition according to claim3, wherein the ratio of the first component is in a range of fromapproximately 20% to approximately 50% by weight, the ratio of thesecond component is in a range of from approximately 15% toapproximately 40% by weight, the ratio of the third component is in arange of from approximately 5% to approximately 35% by weight and theratio of the fourth component is in a range of from approximately 5% toapproximately 30% by weight, based on the total weight of the liquidcrystal compounds.
 7. A liquid crystal composition having a negativedielectric anisotropy consisting essentially of at least one compoundselected from a group of compounds represented by formula (1) as thefirst component, at least one compound selected from a group ofcompounds represented by formula (2) as the second component, at leastone compound selected from a group of compounds represented by formula(3) as the third component and at least one compound selected from agroup of compounds represented by formula (4) as the fourth componentand (5) at least one antioxidant:

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl oralkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or 1,4-phenylene; A²is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenhlene; and Z¹ isa single bond or —COO—.
 8. A liquid crystal composition having anegative dielectric anisotropy consisting essentially of at least onecompound selected from a group of compounds represented by formula (1)as a first component, at least one compound selected from a group ofcompounds represented by formula (2) as a second component, at least onecompound selected from a group of compounds represented by formula (3)as a third component and at least one compound selected from a group ofcompounds represented by formula (4) as a fourth component and (5) anantioxidant represented by formula (8):

wherein R¹ is alkyl or alkenyl; R² is alkyl or alkoxy; R³ is alkyl oralkoxymethyl; R⁴ is alkyl; A¹ is 1,4-cyclohexylene or 1,4-phenylene; A²is 1,4-cyclohexylene, 1,4-phenylene or 2-fluoro-1,4-phenhlene; Z¹ is asingle bond or —COO—; and m is an integer from 1 to 9
 9. The liquidcrystal composition according to claim 7, wherein the ratio of theantioxidant is in a range of from approximately 50 ppm to approximately600 ppm based on the total weight of the liquid crystal compounds. 10.The liquid crystal composition according to claim 8, wherein the ratioof the antioxidant is in a range of from approximately 50 ppm toapproximately 600 ppm based on the total weight of the liquid crystalcompounds.
 11. A liquid display device comprising the liquid crystalcomposition of claim
 1. 12. A liquid display device comprising theliquid crystal composition of claim
 3. 13. A liquid display devicecomprising the liquid crystal composition of claim
 7. 14. A liquiddisplay device comprising the liquid crystal composition of claim 8.